Complications such as restenosis are a recurring problem in patients who have received artherosclerosis therapy in the form of medical procedures such as percutaneous translumenal coronary angioplasty (PTCA). Restenosis is commonly treated by a procedure known as stenting, where a medical device is surgically implanted in the affected artery to prevent it from occluding post procedure.
A stent is typically cylindrical in shape and is usually made from a biocompatible metal, such as cobalt chromium or surgical steel. Most stents are collapsible and are delivered to the occluded artery via a translumenal catheter. The stent is affixed to the catheter and can be either self expanding or expanded by inflation of a balloon inside the stent that is then removed with the catheter once the stent is in place.
Complications that can arise from stent therapy include restenosis and thrombosis. In an effort to overcome these complications, stents may contain a layer or coating of an anti-restenosis drug that is released in a controlled fashion at the stent-implantation site. Typically, the drug is contained in a permanent or bioerodable polymer carrier, as disclosed, for example, in U.S. Pat. No. 5,716,981 issued to Hunter entitled “Anti-angiogenic Compositions and Methods of Use.” Examples of typical therapies that are proposed to be delivered in this manner are antiproliferatives, anticoagulants, anti-inflammatory agents and immunosuppressive agents, although there are many other chemical and biological agents also mentioned in the patent literature. It has been suggested that the polymer carrier with drug may be covered by a porous biodegradable layer that serves to regulate controlled release of the drug into the body, as disclosed for example, in U.S. Pat. Nos. 6,774,278 and 6,730,064.
More recently, stents in which an anti-restenosis drug is carried in channels, grooves or pores for release in “polymer-free” i.e. pure-drug form have been proposed. Alternatively, stents having roughened surface intended to anchor a drug layer on the surface of the stent, for release in pure-drug form have been proposed, for example, in U.S. Pat. Nos. 6,805,898 and 6,918,927. None of these patents show or suggest that with particular classes of anti-restenosis compounds, it is possible to enhance the anti-restenosis activity of the compounds by selection of surface roughness features within certain ranges on the stent surface.
In light of the complications associated with stent therapy, it would be desirable to develop a stent having at least one roughened or textured surface for increased surface area, which can be manufactured in such a way as to maximize structural integrity, drug loading capacity, and ability to deliver drug to the vessel wall in a therapeutically enhanced way, as evidenced by a reduced risk of rate of occurrence or extent of restenosis following stent placement at the site of vascular injury.